Elevated Risk of Thrombotic Events Postpartum Investigated

Thrombosis significantly increases during pregnancy and again during the postpartum period until at least 12 weeks after delivery, according to new research.

Pregnancy significantly increases the risk of thrombosis, rising further during the postpartum period, conventionally defined as the 6 weeks after delivery. It has been unknown whether that risk remains increased after the 6-week postpartum period passes, and guidelines for treatment of thrombotic disorders during pregnancy advise the discontinuation of prophylactic therapy at 6 weeks after delivery in women at high risk for venous thromboembolism.

A new study published in

the Feb. 13, 2014, issue of

was designed to assess the duration of risk of a thrombotic event after delivery in a large population-based cohort of women. Researchers led by Hooman Kamel, MD, of the Department of Neurology at Weill Cornell Medical College, followed 1,687,930 women with a first recorded delivery who were hospitalized for labor and delivery in nonfederal emergency departments and acute care hospitals in California between Jan. 1, 2005, and June 30, 2010. Among the women, 1,015 had a thrombotic event in the period of 1 year plus up to 24 weeks after delivery.

The risk of primary thrombotic events was markedly higher within 6 weeks after delivery than in the same period 1 year later, with 411 events versus 38 events, for an absolute risk difference of 22.1 events per 100,000 deliveries. There was also a modest, but significant, increase in risk during the period of 7 to 12 weeks after delivery compared with the same period 1 year later, with 95 versus 44 events per 100,000 deliveries, for an absolute risk difference of 3.0 events.

The researchers concluded an elevated risk of thrombosis persisted until at least 12 weeks after delivery, but the absolute increase in risk beyond 6 weeks after delivery was low.

the New England Journal of Medicine